Fingerprint dictionary image renewing method

ABSTRACT

A dictionary image renewing method in a fingerprint identification device registers images into a dictionary memory as multiple dictionaries. The method includes extracting images from a plurality of fingerprint images determined as being acceptable identification by mutual identification and using the multiple dictionaries to perform identification processing of entered fingerprint images. This includes successively identifying by comparing entered fingerprint images with the dictionary images registered in the multiple dictionaries, and when identification acceptance results with any one of the multiple dictionaries the one dictionary determined as being identification accepted is renewed to the dictionary image registered in any one of the remaining dictionaries. The remaining multiple dictionaries are renewed to the dictionary image extracted from the entered fingerprint images.

This application is a division of application Ser. No. 08/816,406, filedMar. 5, 1997, now U.S. Pat. No. 5,995,641, which is a 371 ofPCT/JP96/02377, filed on Aug. 26, 1996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for renewing dictionary imagedata in a fingerprint identification device, and particularly to amethod for renewing dictionary images in a fingerprint identificationdevice, in which dictionary identification time can be shortened.

The present invention relates to a method for renewing dictionary imagesin a fingerprint identification device, and particularly to a method forrenewing dictionary images in a fingerprint identification device, inwhich the dictionary images can be kept in the best condition.

The present invention relates to a dictionary registration andidentification method for a fingerprint identification device, andparticularly to a multiple-dictionary registration and identificationmethod for a fingerprint identification device, in which anidentification rate is improved by registering and identifying aplurality of dictionaries.

The present invention relates to a method for judging fingerprinting ina fingerprint identification device, and particularly to afingerprinting judging method in a fingerprint identification device, inwhich continuous identification rejections can be prevented.

The present invention relates to a fingerprint identification devicewhich can prevent misjudgment in identifying a fingerprint and to afingerprinting judging method.

2. Description of the Related Art

In a fingerprint identification device, by identifying an enteredfingerprint image with fingerprint dictionary data previously registeredin a dictionary memory to judge whether or not the entered fingerprintimage corresponds to a finger of a particular person whose dictionarydata is previously registered in the fingerprint identification device.

In such a case, it is desired that time required for dictionaryidentification can be shortened by enabling to quickly identify theconformity with the multiple dictionary data to be used foridentification.

The fingerprint dictionary data is image data of multiple characteristicparts, such as ending points and bifurcation points, of a fingerprintimage extracted by a sensor and registered together with its coordinatedata, and when the entered fingerprint image is detected to conform withsome of such characteristic data, it is determined to be identificationpass.

On the other hand, in fingerprinting by using a sensor, it has beenexperienced that fingerprints are relatively easily deformed dependingon the position of fingers on a fingerprinting surface, the magnitude ofpressing a finger against the fingerprinting surface or the like, andthe fingerprint image to be taken into the fingerprint identificationdevice is varied.

Therefore, if dictionary data is registered as many as possible on thesame person, various cases can be covered even when the fingerprints aredeformed as described above. Adopting a method of determining as anidentification pass when the entered fingerprint image matches with anyone of dictionary images, an identification match rate (acceptance rate)of the fingerprint identification device can be improved.

FIG. 14 shows the configuration of conventional dictionary data, inwhich (a) indicates all dictionary data, (b) dictionary data on oneperson within all dictionary data, and (c) one characteristic data inthe dictionary data on one person.

All dictionary data comprises dictionary data on M to-be-identifiedpersons (1 to M), for example. Dictionary data on one person comprises Nminutiae (minutiae 1 to N), for example. And, one minutia data comprisesimage data on minutiae and its coordinate data in a prescribed window.

In the fingerprint identification device, by using dictionary datahaving N minutia data registered therein, pattern matching is made fromminutia 1 in order with respect to the entered fingerprint image whichis taken in at the fingerprint identification, and if a pattern matcheson, for example, L minutia data, it is determined as identificationpass.

FIG. 15 shows an example of identifying minutiae in which (a) indicatesExample 1, and (b) Example 2. Among N minutiae, those with matchedpatterns are indicated by ∘, and those without matched patterns by Δ.

Example 1 shows that minutia 2 does not match but other minutiae match,and it is determined to be identification pass based on the patternmatching of (L+1) minutiae. And, Example 2 shows that minutiae 2, 3 and5 do not match but other minutiae match, and it is determined to beidentification pass based on the pattern matching of (L+3) minutiae.

Besides, in the fingerprint identification device, to complete theidentification with the dictionary data soon, when N minutiae have Kminutiae which do not have matched patterns in succession, it is judgedthat the entered fingerprint image and the dictionary data are not ofthe same person, it is determined as identification rejection, andidentification of the remaining minutiae with the dictionary data iscanceled.

FIG. 16 shows the cancellation of the identification process, in whichdictionary data comprising N minutiae is identified in succession, K(=3) continuous identification mismatches are detected at minutiae 5through 7, and the process is terminated at this point as identificationrejection. In this case, even if it is possible that there may be aminutia having a matched pattern among, for example, minutia 8 throughminutia N, the remaining process is canceled.

In identifying the minutiae shown in FIG. 15, when minutia data thathave patterns which often do not match with entered fingerprint imagesare contained many in minutia data of less than 1, time required beforepatterns are matched with L minutia data becomes longer than when suchminutia data are not contained.

And, in the cancellation of the identification process shown in FIG. 16,when the minutia data that have patterns which do not match with theentered fingerprint images are contained at least K in succession in theneighborhood of the head of the N minutia data string, an identificationmatch rate (acceptance rate) is lowered.

FIG. 1 shows the configuration of a conventional fingerprintidentification device to which the present invention are applied andwhich comprises a core section 10 and a control 20. The core section 10performs registration and identification of fingerprint images, and thecontrol 20 controls the processing in the core section 10. The control20 sends a command to the core section 10 and receives from the coresection a response to the command.

In the core section 10, reference numeral 11 denotes a centralprocessing unit (CPU) for controlling the processing of registration andidentification of fingerprint images. And, reference numeral 12 denotesa sensor for taking the image of a fingerprint which is to be registeredor identified, 13 a frame memory for storing the image taken from thesensor 12 as a multivalued image, 14 an image processing circuit forprocessing various images, such as binarization of a multivalued image,extraction of minutiae from a binarized image, pattern matching of abinarized image with minutiae and the like, 15 a binary memory forstoring a binarized image, 16 a dictionary memory for storing theminutiae extracted from a binarized image as a dictionary image, and 17an identification memory for keeping the minutiae of fingerprints to beused for identification; and these are connected to a bus 18 of the CPU11. And, reference numeral 19 is a control interface for interfacing ofa command and a response between the bus 18 and the control 20.

As a dictionary registration identifying method in such a fingerprintidentification device, use of a plurality of dictionary images has beenproposed to improve an identification rate.

The dictionary images are minutiae such as ending points and bifurcationpoints extracted from the image of a fingerprint pressed on the sensor,and when some of such characteristics parts are detected to match withthe entered image, it is determined to be identification pass.

On the other hand, in fingerprinting by using a sensor, it has beenexperienced that fingerprints are relatively easily deformed dependingon the position of fingers on a fingerprinting surface, the magnitude ofpressing a finger against the fingerprinting surface or the like, andthe fingerprint image to be taken into the fingerprint identificationdevice is varied.

Therefore, if dictionaries are registered as many as possible on thesame person, various cases can be covered even when the fingerprints aredeformed as described above. Adopting a method of determining as anidentification pass when the entered fingerprint image matches any onein the dictionaries, an identification rate of the fingerprintidentification device can be improved.

FIG. 17 shows a flowchart of registration and identification processingin a conventional multiple dictionary method, in which (a) indicates theregistration processing, and (b) the identification processing.

In the multiple dictionary method, the registration processing isperformed as follows.

1 When a fingerprint is taken, a fingerprint image (first image) enteredthrough the sensor 12 is binarized in the image processing circuit 14through the frame memory 13, and stored in the binary memory 15.

2 From the binarized image stored in the binary memory 15, minutiae areextracted in the image processing circuit 14 by running the minutiaextracting program in the CPU 11 to temporarily register as afingerprint image in the identification memory 17.

3 When a fingerprint is taken again, a fingerprint image (second image)is binarized in the image processing circuit 14 through the sensor 12and the frame memory 13, and stored in the binary memory 15.

4 By running the identification processing program in the CPU 11,pattern matching is performed in the image processing circuit 14 in viewof the dictionary image (first image) temporarily registered in theidentification memory 17 and the binarized image (second image) storedin the binary memory 15.

5 When it is determined to be identification pass as a result ofidentification, the dictionary image for the first image temporarilyregistered is formally registered as dictionary 1 in the dictionarymemory 16.

6 Besides, from the binarized image of the second image stored in thebinary memory 15, the dictionary image, which is obtained by extractingthe minutiae in the image processing circuit 14 by running the minutiaextracting program in the CPU 11, is formally registered as dictionary 2in the dictionary memory 16.

Thus, when the first image and the second image have been registeredformally, it is determined that the registration is success, and theprocessing is terminated. On the other hand, when it is determined asidentification rejection as a result of identification, the processingso far is cleared as a registration failure.

By the multiple dictionary method, the identification processing isperformed as follows.

1 By fingerprinting, a fingerprint image (identification image) enteredthrough the sensor 12 is binarized in the image processing circuit 14through the frame memory 13 and stored in the binary memory 15.

2 According to a command from the control 20, the dictionary image ofdictionary 1 as the dictionary number which is designated from thedictionary memory 16 is transferred to the identification memory 17, andthe matching program in the CPU 11 is performed to make pattern matchingin the image processing circuit 14 by the binarized image in the binarymemory 15 and the dictionary image in the identification memory 17.

3 When the identification is resulted to be identification rejection,the dictionary image of dictionary 2 is used to perform again patternmatching with the binarized image of the binary memory 15 in the imageprocessing circuit 14.

4 When the processing in 2 above results in identification acceptancewith respect to the dictionary image of dictionary 1 or the processingin 3 above results in identification acceptance with respect to thedictionary image of dictionary 2, the result is noticed asidentification success to the control 20.

5 When the processing in 2 and the processing in 3 are resulted inidentification rejection, the results are noticed as identificationfailure to the control 20.

By adopting the multiple dictionary method into the fingerprintidentification device, identification rejection based on the deformationof fingerprints caused at fingerprinting can be prevented, and anidentification rate can be improved.

However, the fingerprint is not always invariable but varies due to thefollowing various causes.

(1) Changes over time (age, external injury on fingers)

(2) Changes of placing fingers due to practice

Therefore, the fingerprint image entered every time varies graduallywith respect to the previously registered dictionary image, and whenfingerprinting is made later, it may result in identification rejection.Therefore, it is hard to keep a high identification rate unless theregistered dictionary image is renewed at an appropriate opportunity.But, a method of renewing the dictionary image which enables the renewalof the dictionary image has not been proposed.

Another dictionary registration and identification method is knowndescribed in, for example, Japanese Patent Laid-Open Publication No. Hei7-271980.

FIG. 18 shows the outline of a fingerprint identification device towhich prior art and the present invention are applied, in whichreference numeral 61 denotes a transparent prism type finger stand, 61aa top thereof, 61b an inclined face, and 61c a bottom face thereof.Reference numeral 62 denotes a prism face on which a finger ispositioned at the top face of the finger stand 61, and 63 a fingerpositioned on the prism face. Reference numeral 64 denotes a lamp toilluminate the finger 63 from below the bottom face 61c of the fingerstand 61. Reference numeral 65 denotes an image pickup device to take apicture of the finger 63 from the side of the inclined face 61b of thefinger stand 61. Reference numeral 66 denotes a fingerprintidentification control for controlling the lamp 64 and the image pickupdevice 65 to identify the fingerprint. In the fingerprint identificationcontrol 66, reference numeral 67 denotes an image processing unit forprocessing the fingerprint image taken from the image pickup device 65,68 a fingerprint registering unit for registering the collectedfingerprint images as the dictionary, and 69 an identifying unit foridentifying the pictured fingerprint image with the registereddictionary images to judge matching.

The prism face 62 of the finger stand 61 is illuminated through thefinger stand 61 from below the bottom face 61c by the lamp 64. Thefinger 63 is put on and pressed against the prism face 62 to contactfingerprint ridges to the prism face 62. When this sate is viewed fromthe inclined face 61b of the finger stand 61, the fingerprint ridgeshave a light reflection factor different from other parts, so that thefingerprint image formed on the prism face 62 can be pictured from theinclined face 61b of the finger stand 61 by the image pickup device 65such as a TV camera.

The pictured fingerprint image is processed by the image processing unit67 in the fingerprint identification control 66 to make it easy tocompare minutiae, and identified by the identifying unit 69 with theminutiae of the fingerprints registered in the form of the dictionaryimage in the fingerprint registering unit 68. And, when a prescribednumber or more of minutiae are detected to match with the enteredfingerprint image, it is judged as identification pass. The minutiae ofthe fingerprint are extracted in view of the ending points andbifurcation points of the fingerprint ridges.

Before starting the identification of a fingerprint, it is necessary tomake sure that the finger 63 is on the finger stand 61. Therefore, afingerprinting judging process is performed to judge that fingerprintinghas been made.

FIG. 19 shows the flowchart of a conventional fingerprinting judgingprocess in the fingerprint identification device. In identifying thefingerprint, the device first requires that the fingerprint is affixed.After determining that the first fingerprinting has been made, afingerprint image is taken and identified with the registeredfingerprint images. When the identification is resulted inidentification pass, processing as identification success is performed,and, for example, prescribed processing such as permission for entranceis made.

When the first fingerprinting results in identification rejection,fingerprinting is required again, and a fingerprint image is taken toperform identification processing. When it results in identificationrejection, the same procedure is repeated, and if the thirdidentification processing results in identification rejection,processing as identification failure is performed, and, for example,processing such as prohibition against entrance is made.

In the conventional fingerprinting judging process shown in FIG. 19,when the identification results in identification rejection,fingerprinting is required again and a fingerprint image is takenaccordingly, the finger on the finger stand remains as it is and kept inclose contact with the fingerprinting surface (prism face 2) through thethree identifications.

When the first identification results in identification rejection andfingerprinting is required again by the fingerprint identificationdevice, if the finger is continuously in close contact with thefingerprinting surface from the first fingerprinting, the fingerprintimage taken upon another requirement for fingerprinting is almost thesame as the fingerprint image taken first. Therefore, when thefirst-taken fingerprint image results in identification rejection, it ishighly possible that the second-taken fingerprint image also results inidentification rejection.

Therefore, in the second fingerprinting, if it is urged that the fingeris separated from the fingerprinting surface after the firstfingerprinting and then positioned on the fingerprinting surface forfingerprinting again, it may be highly possible that the fingerprintimage taken by the second fingerprinting results in identification pass,but such a method has not been adopted.

And, when the finger is positioned on the fingerprinting surface beforethe first fingerprint image collection and kept thereon through aplurality of fingerprint image collections in the same way as by theconventional method, fingerprinting time becomes long, the finger skinstretches or shrinks to deform the fingerprint image, and anidentification rate is lowered. Besides, when the finger on thefingerprinting stand is not in position, the fingerprint is partlydeformed, fingerprinting time becomes long, the fingerprint image isheavily deformed, and an identification rate is lowered.

Since the fingerprint image is taken in immediately after checking thefingerprinting by the device, it is felt that the fingerprint image istaken immediately when the finger is put on the fingerprinting surface.Therefore, when the finger is separated from the fingerprinting surfaceafter each fingerprinting as in the method of the present invention,timing for taking the fingerprint image after fingerprinting can be keptconstant and it can be taken in a short time after fingerprinting, sothat the identification rate at the first fingerprinting and that at thesecond fingerprinting can be kept same by providing the same conditionsfor taking fingerprints. But, such a method has not been proposed.

FIG. 20 is an explanatory view of the fingerprint image pickup unit, inwhich reference numeral 71 denotes a camera, 72 a light source, 73 aprism, 74 an elastic film, and 75 a finger subject to fingerprinting.The camera 71 can be a CCD camera, for example. When it is provided atan angle of critical angle θ or below with respect to the fingerprintingsurface (the surface of the elastic film 74) and the fingerprintingsurface is illuminated through the prism 73 by the light source 72, thereflected light does not enter the camera 71 if the finger 75 is not inposition. And, when the finger 75 is put on the elastic film 74 on thefingerprinting surface, the reflected light which corresponds to theridge and valley lines forming the fingerprint of the finger 75 entersthe camera 71, and a signal of the pictured fingerprint is outputtedfrom the camera 71.

And, the elastic film 74 serves to improve the adhesion with the finger75 and to enable to take a clear picture of the fingerprint of even adry finger, and is required to have abrasion resistance to some extent.And, there is not any colorless transparent material available.Accordingly, when external intense light enters the fingerprintingsurface, scattered light may be produced by the elastic film 74 andentered into the camera 71. And, if the elastic film 74 is scratched ormade dirty, reflected light is produced by the light from the lightsource 72 and entered into the camera 71.

In the fingerprint identification device, the finger 75 is positioned onthe fingerprinting surface (the elastic film 74) and the fingerprint ispictured by the camera 71. And it is necessary to judge whether or notthe image signal from the camera 71 is derived from the fingerprintimage. Therefore, in the conventional fingerprint identification device,for example, a method (a) is known in which when the finger ispositioned on the fingerprinting surface, the reflected light from thefinger enters the camera 71, average luminance within a judging areaused to identify the fingerprint in the pictured screen by the camera 71is determined, and when the average luminance exceeds a predeterminedthreshold, it is presumed that the reflected light from the finger 75has entered the camera 71, it is judged that fingerprinting has beenmade, and the fingerprint image signal at the time is taken to make theregistration or identification of the fingerprint.

A method (b) is also known in which the judging area is divided into aplurality of blocks, and when the number of blocks which have theaverage luminance of respective blocks exceeding a threshold exceeds aprescribed value, it is judged as a fingerprinting state. And, as to thenumber of blocks in the judging area, when it is assumed that the numberof blocks in the judging area is j, the number of picture elements inthe block is m, and luminance of the picture elements in the judgingarea is Pqn, average luminance A q of a certain block is expressed asfollows. ##EQU1## And, a method is also known in which a total of blockssatisfying the average luminance A q larger than a certain threshold ais determined and regarded as N, and when the total N becomes largerthan a certain threshold b, it is judged that fingerprinting has beenmade.

In the conventional method (a) that it is judged that fingerprinting hasbeen made when the average luminance in the judging area exceeds thethreshold, if intense light such as direct sunlight enters thefingerprinting surface, the scattered light from the elastic film 74enters the camera 71 to make the entire picture white, and the averageluminance is increased. In other words, an error is caused in judgingthe fingerprinting.

And, in the conventional method (b) that it is judged thatfingerprinting has been made when numeral N indicating the number oftimes that the average luminance of respective blocks in the judgingarea exceeds the threshold a is determined and exceeds the threshold b,lighting nonuniformity can be compensated, but in the same way as theconventional method (a), the average luminance of respective blocks isincreased when intense light enters the fingerprinting surface, an erroroccurs in judging fingerprinting.

SUMMARY OF THE INVENTION

It is an object of the invention that in a fingerprint identificationdevice, match data at the time of performing multiple number of times ofidentification on all minutia data in dictionary data is stores,priorities are determined according to the match data at a certain timeto arrange the minutia data in a different sequence, so that timerequired to result in identification acceptance is shortened, dictionaryidentification can be made quickly, and an identification match rate(acceptance rate) can be prevented from being lowered due to thecancellation of the identification because of continuous identificationmismatch.

It is another object of the invention that for a fingerprintidentification device, a dictionary image renewing method is provided torenew registered dictionary images to secure the best dictionary imagesall the time, thereby retaining a high identification rate.

It is another object of the invention that in a fingerprintidentification device, multiple dictionaries are registered to performidentification, and at the time of registering, more stable multipledictionary images can be obtained readily, and at the time ofidentifying, the identification processing with the multipledictionaries can be made readily.

It is another object of the invention that for a fingerprintidentification device, a fingerprinting judging method is provided bywhich at the time of capturing a fingerprint image to be identified,fingerprinting is made from a state that a fingerprint has not beenaffixed, the obtained fingerprint image is captured as an image forfingerprint identification, so that identification rejection of theaffixed fingerprint is prevented from being repeated due to thedeformation of the fingerprint caused when the fingerprinting state iscontinued for a long period of time, timing of capturing the fingerprintimage after fingerprinting can be made constant, and the capturing canbe made in a short time of period after fingerprinting.

It is another object of the invention to provide a fingerprintidentification device and a fingerprinting judging method which preventan error in judging fingerprinting.

A dictionary image renewing method in a fingerprint identificationdevice according to the invention has a given number of dictionary datahaving a plurality of arranged minutia data in a fingerprint image,performs pattern matching between an entered fingerprint image and themultiple minutia data in the dictionary data, and detects the matchingbetween the entered fingerprint image and the dictionary data accordingto the matching with a prescribed number of minutia data, wherein matchdata which indicates the number of times of matching with the enteredfingerprint image is provided in the respective minutia data, andarranges the respective minutia data, which form the dictionary data, inthe order from the greater match data when pattern matching is performedbetween all minutia data and the entered fingerprint images for aprescribed period.

In the dictionary image renewing method in a fingerprint identificationdevice according to the invention, dictionary data having a plurality ofminutia data arranged is provided, pattern matching is performed betweenan entered fingerprint image and the multiple minutia data, and thematching between the entered fingerprint image and the dictionary datais detected when a prescribed number of minutia data has matched.

In the dictionary image renewing method in a fingerprint identificationdevice according to the invention, match data which indicates the numberof times of matching with the entered fingerprint image is provided inthe respective minutia data. And, pattern matching is performed betweenall minutia data and the entered fingerprint images for a prescribedperiod and the order of the respective minutia data is arranged in theorder from the greater match data.

By arranging as described above, matching with a prescribed number ofminutia data is accelerated, so that the fingerprint image checking timecan be shortened. And, when the identification processing is canceledowing to the continuous multiple numbers of mismatches inidentification, an identification match rate (acceptance rate) can beprevented from lowering due to the cancellation of identification.

A first dictionary image renewing method in a fingerprint identificationdevice of the present invention registers as dictionaries dictionaryimages extracted from a plurality of fingerprint images determined asidentification acceptance by mutual identification and uses the multipledictionaries to perform identification processing of entered fingerprintimages, wherein the entered fingerprint images are successivelyidentified with the dictionary images registered in the multipledictionaries, and when identification is resulted as acceptance with anydictionaries, one dictionary is renewed to the dictionary imageregistered in the other dictionary, and the other dictionary is renewedto the dictionary image extracted from the input fingerprint image.

A second dictionary image renewing method in a fingerprintidentification device according to the present invention registers asdictionaries dictionary images extracted from a plurality of fingerprintimages determined as identification acceptance by mutual identificationand uses the multiple dictionaries to perform identification processingof entered fingerprint images, wherein the entered fingerprint imagesare successively identified with the dictionary images registered in themultiple dictionaries, and when identification is resulted as acceptancewith both dictionaries, one dictionary is renewed to the dictionaryimage registered in the other dictionary, and the other dictionary isrenewed to the dictionary image extracted from the input fingerprintimage; and when identification is resulted as acceptance with onedictionary and rejection with the other dictionary, the dictionary whichis resulted in the rejection is renewed to the dictionary imageextracted from the entered fingerprint image.

A third dictionary image renewing method in a fingerprint identificationdevice according to the present invention registers as dictionariesdictionary images extracted from a plurality of fingerprint imagesdetermined as identification acceptance by mutual identification anduses the multiple dictionaries to perform identification processing ofentered fingerprint images, wherein the entered fingerprint images aresuccessively identified with the dictionary images registered in themultiple dictionaries, and when identification is resulted as acceptancewith any dictionaries, dictionaries other than one registered first arerenewed to the dictionary image extracted from the entered fingerprintimage.

A fourth dictionary image renewing method in a fingerprintidentification device according to the present invention registersdictionary images extracted from multiple fingerprint images which havebeen judged as acceptance by mutual identification as a main dictionaryand a sub-dictionary and uses the main dictionary to performidentification processing of an entered fingerprint image, wherein whenthe entered fingerprint image is identified with the main dictionary,identification with the sub-dictionary is also performed to renew anidentification match rate of each dictionary, and the sub-dictionary isreplaced by the main dictionary when the identification match rate ofthe sub-dictionary exceeds the identification match rate of the maindictionary.

In the first dictionary image renewing method in a fingerprintidentification device of the present invention, the dictionary imagesextracted from the plurality of fingerprint images determined asidentification acceptance by mutual identification are registered asdictionaries into a dictionary memory, and these multiple dictionariesare used to identify the entered fingerprint images.

In this case, the entered fingerprint images are successively identifiedwith the dictionary images registered in the multiple dictionaries, andwhen identification is resulted as acceptance with any dictionaries, onedictionary is renewed to the dictionary image registered in the otherdictionary, and the other dictionary is renewed to the dictionary imageextracted from the input fingerprint image.

In the first dictionary image renewing method in a fingerprintidentification device of the present invention, since the fingerprintidentification device always has optimum dictionary images as thedictionary, a high identification rate can be retained, so that anidentification rate in the fingerprint identification device can beimproved.

In the second dictionary image renewing method in a fingerprintidentification device of the present invention, for the fingerprintidentification device having a multiple dictionary method same as thefirst dictionary image renewing method, the entered fingerprint imagesare successively identified with the dictionary images registered in themultiple dictionaries, and when identification is resulted as acceptancewith both dictionaries, one dictionary is renewed to the dictionaryimage registered in the other dictionary, and the other dictionary isrenewed to the dictionary image extracted from the input fingerprintimage in the same way as the first dictionary image renewing method.

And, when identification is resulted as acceptance with one dictionaryand rejection with the other dictionary, the dictionary which isresulted in the rejection is renewed to the dictionary image extractedfrom the entered fingerprint image.

In the second dictionary image renewing method of the present invention,since the fingerprint identification device always has optimumdictionary images as the dictionary, a high identification rate can beretained, so that an identification rate in the fingerprintidentification device can be improved.

In the third dictionary image renewing method in a fingerprintidentification device according to the present invention, for thefingerprint identification device having a multiple dictionary methodsame as the first dictionary image renewing method, the enteredfingerprint images are successively identified with the dictionaryimages registered in the multiple dictionaries, and when identificationis resulted as acceptance with any dictionaries, dictionaries other thanone registered first are renewed to the dictionary image extracted fromthe entered fingerprint image.

In the third dictionary image renewing method in a fingerprintidentification device according to the present invention, for thefingerprint identification device, since the fingerprint identificationdevice always has optimum dictionary images as the dictionary, a highidentification rate can be retained, so that an identification rate inthe fingerprint identification device can be improved.

In the fourth dictionary image renewing method in a fingerprintidentification device according to the present invention, for thefingerprint identification device, the dictionary images extracted fromthe multiple fingerprint images which have been judged as acceptance bythe mutual identification are registered as the main dictionary and thesub-dictionary, and the main dictionary is used to perform theidentification processing of an entered fingerprint image.

In this case, when the fingerprint image is identified with the maindictionary, the identification with the sub-dictionary is also performedto renew the identification match rate of each dictionary. And thesub-dictionary is replaced by the main dictionary when theidentification match rate of the sub-dictionary exceeds theidentification match rate of the main dictionary.

In the fourth dictionary image renewing method in a fingerprintidentification device according to the present invention, for thefingerprint identification device, since the dictionary images arerenewed to keep a high match rate all the time, the dictionary imageswith higher reliability can be obtained as renewed.

A multiple dictionary registration and identification method in afingerprint identification device according to the present inventioncomprises a binary memory for holding a binarized input fingerprintimage, a minutia extracting means for extracting minutiae from thebinarized fingerprint image, a dictionary memory for registering theextracted minutiae as an dictionary image, an identification memory forholding minutiae to be identified, and an identifying means foridentifying the binarized image held in the binary memory with theminutiae held in the identification memory, wherein a plurality offingerprint images on the same finger are mutually identified at thetime of registering the dictionary image, the minutiae of thefingerprint image identified as acceptance are registered in thedictionary memory as a dictionary image, and at the time of identifyingthe entered fingerprint, the entered fingerprint image is identifiedwith the multiple dictionary images, and when identification with anydictionary image results in acceptance, the input fingerprint is judgedas identification success.

In the multiple dictionary registration and identification method in afingerprint identification device according to the present invention,the fingerprint identification device has the binary memory to keepbinarized entered fingerprint images, the minutia extracting means toextract the minutiae from the binarized fingerprint images, thedictionary memory to register the extracted minutiae as the dictionaryimage, the identification memory to keep the minutiae to be identified,the identification means to identify the binarized image held in thebinary memory with the minutiae held in the identification memory.

In this case, to register the dictionary image, the minutiae extractedby the minutia extracting means from the first fingerprint image kept bythe identification memory and the binarized image of the secondfingerprint image on the same finger kept by the binary memory areidentified by the identification means, and when determined asidentification acceptance, the minutiae of the first fingerprint imageand the minutiae extracted by the minutia extracting means from thesecond fingerprinting image are registered in the dictionary memory asthe first and second dictionary images.

And, at the time of identifying the entered fingerprint, the binarizedimage of the entered fingerprint image kept in the binary memory isidentified with the first dictionary image kept in the identificationmemory, and when determined as identification rejection, it isidentified again with the second dictionary image, and whenidentification with any dictionary image results in identificationacceptance, it is judged that the input fingerprint is identified with afingerprint image previously registered in the fingerprintidentification device and judged as identification success.

Besides, the dictionary images to be registered and identified are notlimited to the first and second dictionary images described above andcan be prescribed multiple numbers. According to the present invention,an identification rate can be improved by registering and identifyingmultiple dictionaries in the fingerprint identification device.

A fingerprinting judging method in a fingerprint identification deviceaccording to the present invention which identifies a fingerprint imagetaken from a fingerprint with dictionary images to judge its conformity,which comprises checking the presence or not of fingerprinting at thebeginning of identification processing, and when the fingerprinting hasbeen made at the beginning of the identification processing, requiringto release a finger, checking the presence or not of fingerprintingafter requiring to release the finger, and when it is confirmed by bothof the above checks for the presence of fingerprinting thatfingerprinting has not been made, requiring to affix a fingerprint,checking again the presence or not of fingerprinting after requiring toaffix the fingerprint, and when the fingerprinting is confirmed as aresult of the rechecking for fingerprinting, capturing a fingerprintimage.

In the fingerprinting judging method in a fingerprint identificationdevice according to the present invention, the fingerprint image takenfrom an affixed fingerprint is identified with the registered dictionaryimages to determine as identification acceptance or rejection.

The fingerprinting judging method in a fingerprint identification deviceaccording to the present invention has the following steps for fingerprinting judgment.

(1) The presence of fingerprinting is judged in the first step of theidentification processing.

(2) When the fingerprinting has been made in the first step of theidentification processing, it is demanded to separate the finger.

(3) After issuing the demand for the finger separation, the presence offingerprinting is judged.

(4) When it is checked in both (1) and (2) above that the fingerprintinghas not been made, a demand for fingerprinting is issued.

(5) After demanding the fingerprinting, the presence of fingerprintingis judged again.

(6) When it is confirmed that fingerprinting has been made as a resultof judging the fingerprinting again after demanding the fingerprintingin (5) above, the fingerprint image is captured.

Therefore, according to the fingerprinting judging method in thefingerprint identification device of the present invention, inaccordance with the result of identifying a fingerprint in thefingerprint identification device, it can be controlled to preventidentification rejection from continuing.

A fingerprint identification device comprises a fingerprint image pickupunit which receives reflected light from a light source to take apicture; an in-block average luminance calculation unit which divides afingerprint judging area into a plurality of blocks and calculatesaverage luminance within the blocks according to a multivalued imagesignal from the fingerprint image pickup unit; a luminance deviationcalculation and arrangement unit which determines deviation between thein-block average luminance from the in-block average luminancecalculation unit and the luminance of each picture element in thejudging area to determine the number of picture elements correspondingto the deviation; a fingerprinting judging unit which judges thatfingerprinting has been made for the fingerprint image pickup unit whenthe number of picture elements within a prescribed range with thedeviation near zero does not exceed a threshold for the number ofpicture elements corresponding to the deviation from the luminancedeviation calculation and arrangement unit; and a fingerprintidentification unit which identifies the fingerprint based on themultivalued image signal from the fingerprint image pickup unit when thefingerprinting judging unit has judged the fingerprinting state.

A fingerprinting judging method in a fingerprint identification deviceaccording to the present invention comprises determining averageluminance for every plurality of blocks in a fingerprint judging areabased on a multivalued image signal pictured by a fingerprint imagepickup unit, determining deviation between the average luminance of theevery block and the luminance of picture elements in the blocks,determining the number of picture elements corresponding to thedeviation in the judging area as the whole, judging whether the numberof picture elements in a prescribed range exceeds a threshold with apoint shifted from the point of deviation zero in the direction of thehorizontal axis by a prescribed value when the deviation is on thehorizontal axis and the number of picture elements on the vertical axis,and when it does not exceed, judging that fingerprinting has been made.

In the fingerprint identification according to the present invention, amultivalued image signal from the fingerprint image pickup unit having aCCD camera is added to an in-block average luminance calculation unitthrough an interface, the in-block average luminance calculation unitdivides the judging area in the image pickup area into a plurality ofblocks and calculates average luminance within each block. The luminancedeviation calculation and arrangement unit determines deviation betweenthe in-block average luminance and the luminance of each picture elementwithin the pertinent block to process all picture elements in thejudging area, and correspondence between the deviation and the number ofpicture elements is determined. The fingerprinting judging unit, whenthe number of picture elements within a prescribed range with thedeviation near zero exceeds a threshold, judges that external light hasentered the fingerprint image pickup unit, and when it does not exceed,judges that fingerprinting has been made with respect to the fingerprintimage pickup unit, binarizes in the binarizing unit the multivaluedimage signal from the fingerprint image pickup unit at this time,identifies it in the fingerprint identifying unit with the binarizedregistered fingerprint in the memory, and outputs the judgment onidentification.

In the fingerprinting judging method in the fingerprint identificationdevice according to the present invention, average luminance isdetermined on every multiple blocks in the fingerprint judging area,deviation between the luminance of each picture element in the block andthe in-block average luminance is determined, and the relation betweenthe deviation and the number of picture elements in the entire judgingarea is determined. And, with the deviation on the horizontal axis andthe number of picture elements on the vertical axis, when the externallight enters or when the incident light into the fingerprint imagepickup unit is small reflected light only, molt of the picture elementshave deviation of zero or close thereto with respect to the in-blockaverage luminance, and the number of picture elements close to thedeviation zero increases to exceed the threshold. On the other hand, inthe fingerprinting state, the reflected light corresponding to thefingerprint enters the fingerprint image pickup unit, so that the numberof picture elements close to the deviation zero decreases, thedistribution of picture elements has a bimodal characteristic with theneighborhood of the deviation zero as the center, and the number ofpicture elements in the neighborhood of the deviation zero does notexceed the threshold. And, in contrast to the electrical characteristicsof the fingerprint image pickup unit and the structures of respectiveunits, the dispersion characteristic of picture elements with respect tothe deviation does not have a symmetric property with the deviation zeroas the center, and with a point shifted from the point of deviation zeroin the direction of the horizontal axis by a prescribed value as thecenter, it is judged whether the number of picture elements in aprescribed range has exceeded the threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a structural example of the fingerprintidentification device to which the present invention is applied.

FIG. 2 is a diagram showing the configuration of dictionary data in oneembodiment of a dictionary image renewing method in the fingerprintidentification method according to the invention, in which (a) shows alldictionary data, (b) one-person dictionary data in the all dictionarydata, and (c) one minutia data in the one-person dictionary data.

FIG. 3 is an explanatory view of arranging minutiae in a differentsequence.

FIG. 4 is diagrams showing one embodiment of a dictionary image renewingmethod in the fingerprint identification device according to theinvention, in which (a) is a flowchart, and (b) is an explanatorydiagram of renewing the contents of each dictionary.

FIG. 5 is diagrams showing one embodiment of a dictionary image renewingmethod in the fingerprint identification device according to theinvention, in which (a) is a flowchart, and (b) is an explanatorydiagram of renewing the contents of each dictionary.

FIG. 6 is diagrams showing one embodiment of a dictionary image renewingmethod in the fingerprint identification device according to theinvention, in which (a) is a flowchart, and (b) is an explanatorydiagram of renewing the contents of each dictionary.

FIG. 7 is a diagram showing the principle configuration of a multipledictionary registration and identification method in the fingerprintidentification device according to the invention.

FIG. 8 is a diagram showing one embodiment of a multiple dictionaryregistration and identification method in the fingerprint identificationdevice according to the invention, in which (a) is a registrationprocessing, and (b) shows an identification processing.

FIG. 9 is a flowchart showing one embodiment of a fingerprinting judgingmethod in the fingerprint identification device according to theinvention.

FIG. 10 is an explanatory diagram of the fingerprint identificationdevice in one embodiment of the fingerprint identification device andfingerprinting judging method according to the invention.

FIG. 11 is a flowchart showing one embodiment of the fingerprintingjudging method according to the invention.

FIG. 12 is an explanatory diagram of a judging area.

FIG. 13 is an explanatory diagram of fingerprinting judging in anembodiment according to the invention.

FIG. 14 is a diagram showing the configuration of conventionaldictionary data, in which (a) shows all dictionary data, (b) one-persondictionary data in the all dictionary data, and (c) one minutia data inthe one-person dictionary data.

FIG. 15 is a diagram showing an example of identifying minutiae, inwhich (a) shows example 1 and (b) shows example 2.

FIG. 16 is a diagram of explaining the cancellation of identificationprocessing.

FIG. 17 is a diagram showing flowcharts of registration andidentification processing by a conventional multiple dictionary method,in which (a) is a registration processing, and (b) shows anidentification processing.

FIG. 18 is a diagram showing the outline of a conventional fingerprintidentification device to which the present invention is applied.

FIG. 19 is a flowchart showing a conventional fingerprinting judgmentprocessing in the fingerprint identification device.

FIG. 20 is an explanatory diagram of a fingerprint picturing unit.

BEST MODE FOR CARRYING OUT THE INVENTION EMBODIMENT 1

FIG. 1 shows one embodiment of a dictionary image renewing method in thefingerprint identification device according to the present invention isapplied. The fingerprint identification device comprises a core section10 in which a fingerprint image is registered and identified and acontrol 20 to control the processing in the core section 10. The controlby the control 20 is performed by sending a command to the core section10 and receives from the core section 10 a response to the command.

In the core section 10, reference numeral 11 denotes a centralprocessing unit (CPU) for controlling the processing of registration andidentification of fingerprint images. And, reference numeral 12 denotesa sensor for taking the image of a fingerprint which is to be registeredand identified. Reference numeral 13 denotes a frame memory for storingthe fingerprint image taken from the sensor 12 as a multivalued image.Reference numeral 14 denotes an image processing circuit for variousprocessing of images, such as binarization of a multivalued image readfrom the frame memory 13, extraction of minutiae from the binarizedimage, pattern matching of the binarized image with the minutia data inthe dictionary data and the like.

Reference numeral 15 denotes a binary memory for storing a binarizedimage. Reference numeral 16 denotes a dictionary memory for storing theminutia data extracted from the binarized image as dictionary data.Reference numeral 17 is an identification memory for keeping the minutiadata of fingerprints to be used for identification. Reference numeral 18denotes a bus of the CPU 11 to connect respective parts to the CPU 11.And, reference numeral 19 is a control interface for interfacing of acommand and a response between the bus 18 and the control 20.

FIG. 2 shows the configuration of dictionary data according to theinvention, in which (a), (b) and (c) correspond to those in FIG. 14except that in the method according to the invention, matching dataindicating a match with an entered fingerprint image is contained ineach minutia data.

Identification processing of a fingerprint image according to the methodof this invention is performed as follows. First, a command of startingthe identification processing is sent from the control 20, and it isread by the core section 10. Then, when a to-be-identified person puts afinger on the sensor 12, a fingerprint image is entered from the sensor12, and it is taken as a multivalued image into the frame memory 13.

The image processing circuit 14 binarizes the multivalued image whichhas been taken into the frame memory 13, stores it in the binary memory15, and transfers the dictionary data with dictionary number designatedby the control 20 from the dictionary memory 16 to the identificationmemory 17. And, pattern matching is performed between the binarizedimage read from the binary memory 15 and the dictionary data read fromthe identification memory 17 in order of minutia 1 to minutia N.

In the core section 10, such identification processing is performedsequentially on N number of minutia data, and when L number of minutiadata are matched, it is determined as identification pass, and a signalof the completion of identification processing is sent to the control20.

Besides, in the core section 10, all N number of minutia data areidentified, and when patterns are matched, the matched data areincreased. The control 20 checks the magnitude of matched data withrespect to respective minutia data at a certain time, and changes thearranged order of respective minutia data in order of larger to smallermatched data. Such processing is repeated on every prescribed number ofidentification processing, for example.

FIG. 3 explains the arrangement of minutiae in a different sequence, inwhich (a) shows a state before sorting, and (b) a state after sorting.It shows that the dictionary shown in (a) registered in the fingerprintidentification device is identified a plurality of times, all minutiaeare assigned priorities, and respective minutiae are sorted according tothe priorities, resulting in the order as shown in (b).

After arranging the minutia data in the dictionary data in a differentsequence as described above, the minutia data in the dictionary data isarranged in an optimum order, so that the minutia data closer to thehead of the dictionary data rarely result in identification mismatch inthe identification processing of the entered fingerprint image aftersorting. Therefore, it is assumed that identification pass can beobtained mostly by pattern matching with the L-th minutia data.

And, as a result of such sorting, the minutia data closer to the head ofthe dictionary data have lower possibility of continuous occurrence ofidentification mismatch. Therefore, lowering of an identification matchrate (acceptance rate) is lowered because the identification processingis canceled owing to the continuous occurrence of identificationmismatch with K number of minutia data.

EMBODIMENT 2

FIG. 4 shows one embodiment of a dictionary image renewing method in thefingerprint identification device according to the invention,particularly showing a dictionary image renewing method by the latestfingerprint image determined as identification pass, in which (a) is aflowchart, and (b) is an explanatory diagram of renewing the contents ofeach dictionary.

In FIG. 4, (1) to (7) show respective steps in the dictionary renewingprocessing. It is assumed that dictionary image A is registered indictionary 1 and dictionary image B in dictionary 2 in the followingprocessing.

(1) It is assumed that fingerprint image C is entered by fingerprintingin the identification processing.

(2) First, identification processing with the fingerprint image C isperformed using the dictionary image A of the dictionary 1.

(3) When the identification processing using the dictionary 1 results inidentification rejection, the identification processing with thefingerprint image C is performed using the dictionary image B of thedictionary 2.

(4) If the identification processing using the dictionary 1 and thedictionary 2 results in identification rejection, it is determined asidentification failure, and the dictionary image is not renewed.

(5) If one of the identification processing using the dictionary image Aof the dictionary 1 and the identification processing using thedictionary image B of the dictionary 2 results in identification pass,it is determined as identification success.

(6) The minutiae are extracted from the fingerprint image C andregistered as a dictionary image.

(7) The dictionary images are renewed.

In this dictionary image renewing method, the content of the dictionary1 is changed from the previously registered dictionary image A to thedictionary image B registered in the dictionary 2, and the content ofthe dictionary 2 from the previously registered dictionary image B tothe new dictionary image C as shown in FIG. 4 (b).

In this embodiment, the contents of the dictionary 1 and the dictionary2 are always the latest dictionary images, and even if the fingerprintform, the way of positioning a finger or the like changes gradually, thefingerprint identification device can keep a high identification ratebecause the dictionary image also changes accordingly.

EMBODIMENT 3

FIG. 5 shows one embodiment of a dictionary image renewing method in thefingerprint identification device of the invention, particularly showinga dictionary image renewing method by the latest fingerprint imagedetermined as identification pass, in which (a) is a flowchart, and (b)is an explanatory diagram of renewing the contents of each dictionary.

In FIG. 5 (a), (1) to (7) show respective steps in the dictionaryrenewing processing.

In FIG. 5 (b), ∘ indicates identification pass, and Δ indicatesidentification rejection.

It is assumed that dictionary image A is registered in dictionary 1 anddictionary image B in dictionary 2 in the following processing.

(1) It is assumed that fingerprint image C is entered by fingerprintingin the identification processing.

(2) First, identification processing with the fingerprint image C isperformed using the dictionary image A of the dictionary 1.

(3) When the identification processing using the dictionary 1 results inidentification pass or identification rejection, the identificationprocessing with the fingerprint image C is performed using thedictionary image B of the dictionary 2.

(4) If the identification processing using the dictionary 1 and thedictionary 2 results in identification rejection, it is determined asidentification failure, and the dictionary image is not renewed.

(5) If both of the identification processing using the dictionary imageA of the dictionary 1 and the identification processing using thedictionary image B of the dictionary 2 result in identification pass orone of the identification processing using the dictionary image A of thedictionary 1 and the identification processing using the dictionaryimage B of the dictionary 2 results in identification pass, it isdetermined as identification success.

(6) The minutiae are extracted from the fingerprint image C andregistered as a dictionary image.

(7) The dictionary images are renewed.

In this dictionary image renewing method, when both of theidentification processing by the dictionary image A of the dictionary 1and the identification processing by the dictionary image B of thedictionary 2 result in identification pass as shown in FIG. 5 (b), thecontent of the dictionary 1 is changed from the previously registereddictionary image A to the dictionary image B registered in thedictionary 2, and the content of the dictionary 2 from the previouslyregistered dictionary image B to the new dictionary image C in the sameway as in Embodiment 2.

And, when one of the identification processing using the dictionaryimage A of the dictionary 1 and the identification processing using thedictionary image B of the dictionary 2 results in identification pass,the content of the dictionary which has resulted in identificationrejection is renewed to the new dictionary image C.

In this embodiment, the contents of the dictionary 1 and the dictionary2 are always the latest dictionary images, and even if the fingerprintform, the way of positioning a finger or the like changes gradually, thefingerprint identification device can keep a high identification ratebecause the dictionary image also changes accordingly.

EMBODIMENT 4

FIG. 6 shows one embodiment of a dictionary image renewing method in thefingerprint identification device of the invention, particularly showinga method of keeping the content of the first dictionary with the firstlyregistered dictionary image and having the content of the seconddictionary as the dictionary image according to the latest fingerprintimage of identification pass, in which (a) is a flowchart, and (b) anexplanatory diagram of renewing the contents of respective dictionaries.

In FIG. 6 (a), (1) to (7) show respective steps in the dictionaryrenewing processing.

It is assumed that dictionary image A is registered in dictionary 1 anddictionary image B in dictionary 2 in the following processing.

(1) It is assumed that fingerprint image C is entered by fingerprintingin the identification processing.

(2) First, identification processing with the fingerprint image C isperformed using the dictionary image A of the dictionary 1.

(3) When the identification processing using the dictionary 1 results inidentification rejection, the identification processing with thefingerprint image C is performed using the dictionary image B of thedictionary 2.

(4) If the identification processing using the dictionary 1 and thedictionary 2 results in identification rejection, it is determined asidentification failure, and the dictionary image is not renewed.

(5) If one of the identification processing using the dictionary image Aof the dictionary 1 and the identification processing using thedictionary image B of the dictionary 2 results in identification pass,it is determined as identification success.

(6) The minutiae are extracted from the fingerprint image C andregistered as a dictionary image.

(7) The dictionary images are renewed.

In this dictionary image renewing method, the content of the dictionary1 is kept as the previously registered dictionary image A, and thecontent of the dictionary 2 is changed from the previously registereddictionary image B to the new dictionary image C as shown in FIG. 6 (b).

In this embodiment, the content of the first dictionary remains same,but the content of the second dictionary is always the latest dictionaryimage. And, even if an accidental change occurs in the fingerprint formdue to an external injury or the like, when it is determined asidentification pass once, its content is renewed, and as the externalinjury cures, the renewal is made accordingly, and the dictionary isrenewed according to the change of the fingerprint form until it returnsto the original form. Therefore, in this embodiment, even when thefinger form changes, the dictionary image changes accordingly, so that ahigh identification rate can be kept. And, since the content of thefirst dictionary does not change, it is highly possible that the firstdictionary has a higher identification rate when the fingerprint formhas fully returned to the original state. The method of this embodimentis effective against not only an external injury but also changes withage and a way of positioning a finger.

EMBODIMENT 5

As one embodiment of a dictionary image renewing method in thefingerprint identification device according to the invention,description will be made of a dictionary image renewing method using amain dictionary and a sub-dictionary according to the latest fingerprintimage which has been determined as identification pass.

The main dictionary is a dictionary used for identification processing,and the sub-dictionary which is managed together with the maindictionary is a dictionary not used for identification processing.

In this embodiment, the dictionary image is renewed according to thefollowing procedure for identification processing.

(1) A fingerprint image is entered by fingerprinting.

(2) The main dictionary is used to make identification processing withthe entered fingerprint image and to judge acceptance or rejection.

(3) Identification processing is made with all sub-dictionaries todetect matching or mismatching.

(4) The matched result is added to the identification match rate of theexisting sub-dictionary to renew and record.

(5) Through several times of identification processing, when there is asub-dictionary having a match rate higher than the match rate of themain dictionary at some point in time, its content is renewed into themain dictionary.

In this embodiment, the main dictionary for judging identificationacceptance by identification processing can be always kept as adictionary having the highest match rate.

When there are a plurality (n) of main dictionaries and any of the maindictionaries matches in judging acceptance, identification is determinedto be acceptance, and in renewing the dictionary, all sub-dictionarieshaving a match rate higher than the match rates of the main dictionariesare determined as the main dictionaries, and if the number of suchsub-dictionaries is more than n, n number of sub-dictionaries having ahigh match rate may be selected as the main dictionary.

And, a sub-dictionary can be produced from the image taken in every newidentification processing at the time of renewing the main dictionary.Thus, new images can be provided as candidates for the main dictionarywhenever necessary.

The dictionary image renewed in this embodiment always have a highermatch rate, and renewal never lowers a match rate. Therefore, adictionary image having higher reliability can be obtained wheneverrenewed.

EMBODIMENT 6

FIG. 7 shows the principle configuration of a multiple dictionaryregistration and identification method in the fingerprint identificationdevice according to the invention. The configuration of the fingerprintidentification device to which the present invention is applied is thesame as one shown in FIG. 1. As to respective elements shown in theprinciple structure of the present invention, a binary memory 31corresponds to the binary memory 15 shown in FIG. 1, a minutiaextracting means 32 to the image processing circuit 14, the CPU 11 andthe minutia extracting program in the CPU 11, a dictionary memory 33 tothe dictionary memory 16, an identification memory 34 to theidentification memory 17, and an identification means 35 to the CPU 11and the identification processing program in the CPU 11.

FIG. 8 is one embodiment of the present invention, showing flowcharts ofregistration processing and identification processing in the fingerprintidentification device using multiple dictionaries, in which (a) is aregistration processing, and (b) shows an identification processing.

The registration processing in this embodiment is performed as follows.

1 In the same way as the prior art (1) shown in FIG. 17, when afingerprint is taken, a fingerprint image (first image) entered throughthe sensor 12 is binarized in the image processing circuit 14 throughthe frame memory 13, and stored in the binary memory 15.

2 In the same way as the prior art (2) shown in FIG. 17, from thebinarized image stored in the binary memory 15, minutiae are extractedin the image processing circuit 14 by running the minutia extractingprogram in the CPU 11 to temporarily register as a dictionary image inthe identification memory 17.

3 In the same way as the prior art (3) shown in FIG. 17, when afingerprint is taken again, a fingerprint image (second image) isbinarized in the image processing circuit 14 through the sensor 12 andthe frame memory 13, and stored in the binary memory 15.

4 In the same way as the prior art (4) shown in FIG. 17, by running theidentification processing program in the CPU 11, pattern matching isperformed in the image processing circuit 14 in view of the dictionaryimage (first image) temporarily registered in the identification memory17 and the binarized image (second image) stored in the binary memory15.

5 When it is determined to be identification pass as a result ofidentification, the dictionary image for the first image temporarilyregistered is formally registered as dictionary 1 in the dictionarymemory 16.

6 Besides, from the binarized image of the second image stored in thebinary memory 15, the dictionary image, which is obtained by extractingthe minutiae in the image processing circuit 14 by running the minutiaextracting program in the CPU 11, is formally registered as dictionary 2in the dictionary memory 16.

7 Upon the formal registration of the first image and the formalregistration of the second image, it is determined as registrationsuccess and the processing is terminated.

8 When it is determined as identification rejection as a result ofidentification, the processing so far is cleared as a registrationfailure.

The identification processing in this embodiment is performed asfollows.

1 In the same way as the prior art (1) shown in FIG. 17, byfingerprinting, a fingerprint image (identification image) enteredthrough the sensor 12 is binarized in the image processing circuit 14through the frame memory 13 and stored in the binary memory 15.

2 In the same way as the prior art (2) shown in FIG. 17, according to acommand from the control 20, the dictionary image of dictionary 1 as thedictionary number which is designated from the dictionary memory 16 istransferred to the identification memory 17, and the identificationprocessing program in the CPU 11 is performed to make pattern matchingin the image processing circuit 14 by the binarized image in the binarymemory 15 and the dictionary image in the identification memory 17.

3 When the identification processing results in identificationrejection, the dictionary image of the dictionary 2 is used to makepattern matching with the binarized image in the binary memory 15 againin the image processing circuit 14.

4 When the identification with the dictionary image of the dictionary 1by the processing in 2 above or results in acceptance or theidentification with the dictionary image of the dictionary 2 by theprocessing in 3 above results in acceptance, it is determined asidentification success and notified to the control 20.

5 If both processing in 2 and 3 above result in identificationrejection, it is determined as identification failure and notified tothe control 20.

The dictionary images are characteristic parts such as ending points andbifurcation points extracted from the image of a fingerprint pressed onthe sensor, and when some of such minutiae are detected to match withthe entered image, it is determined to be identification pass. But, evenwhen the person and the fingerprint are not different, the dictionaryimage to be obtained is changed due to very slight displacement of thefinger on the fingerprinting surface of the sensor or the magnitude of aforce applied for fingerprinting, and the same result is not alwaysobtained. Therefore, the second image which has been determined asidentification acceptance by the method of this invention generally doesnot become the same dictionary image as the first image.

However, the second image is determined as identification acceptancewith respect to the first image, so that both the first image and thesecond image are considered to be within the image which will be alwaysobtained when the respective fingerprints are fingerprinted. Therefore,the dictionary 1 and the dictionary 2 obtained from the first image andthe second image are considered to be stable dictionary images.

Accordingly, when fingerprint identification is performed using suchmultiple dictionary images obtained as described above, identificationwith any dictionary image is determined as acceptance, and it isdetermined as fingerprint identification success, then an identificationrate can be improved. In this method according to the invention, thedictionary images are not limited to two as shown in the embodiment ofFIG. 7, but can be three or more.

EMBODIMENT 7

FIG. 9 shows a flowchart of one embodiment of a fingerprinting judgingmethod in the fingerprint identification device according to theinvention. The fingerprint identification device used in this embodimentis generally same to the one shown in FIG. 18.

(1) First, the presence of fingerprinting is judged in the first step ofthe identification processing. The presence of fingerprinting can bejudged in view of the fact that when a finger is in a fingerprintingposition, the image detected by the image pickup device is bright by thereflection of light on the finger tip face, while the image is dark whenthe finger is not in the fingerprinting position.

(2) When it is judged in the first step of the identification processingthat the fingerprinting has been made, it is required to separate thefinger from the fingerprinting surface.

(3) After issuing the instructions for separating the finger as in (2)above, the presence of fingerprinting is judged in succession.

(4) When it is checked in (1) above that the fingerprinting has not beenmade from the beginning or checked in (3) above that the fingerprintinghas not been made after giving the instructions for separating thefinger, instructions for fingerprinting are issued again.

(5) After demanding the fingerprinting in (4) above, the presence offingerprinting is judged again in succession.

(6) When it is confirmed that fingerprinting has been made as a resultof judging the fingerprinting again after demanding the fingerprintingin (5) above, the fingerprint image is captured at that point of time.

(7) Using the fingerprint image captured in (6) above, identificationwith the dictionary images is performed.

(8) When the identification processing in (7) above results inacceptance, the step goes to the identification success processing. Whenthe identification processing results in rejection, the step returns to(1) above, it is checked again that fingerprinting has not been made,and the procedure for identification processing is repeated afterfingerprinting. When the third identification processing results inrejection, the step goes to the identification failure processing.

According to this embodiment, when the finger is in position from thebeginning to take the fingerprint image to be identified by thefingerprint identification device or it is kept in position continuouslyfrom the time it was judged as identification rejection, the fingerprintimage of such a finger is not captured as the fingerprint image foridentification processing after that.

Therefore, it can be prevented that even when the finger of which thefingerprint has been determined as identification rejection iscontinuously held for fingerprinting, almost the same fingerprint imageas the fingerprint image which has been judged as rejection is taken asthe next fingerprint image to be identified, and it is determined asrejection again.

And, regardless of the presence or not of fingerprinting before theidentification processing, this embodiment starts to fingerprint from astate that a finger is not touched, and takes a fingerprint imageimmediately after that, so that the fingerprint image is captured withprescribed timing after fingerprinting and in short time of period.Therefore, it is possible to prevent lowering of an identification ratedue to the deformation of the fingerprint image caused by the stretchedor shrunk finger skin which is caused when the finger is in position forfingerprinting before the first identification is performed.

EMBODIMENT 8

FIG. 10 is an explanatory diagram of one embodiment of the fingerprintidentification device according to the invention, in which referencenumeral 41 denotes a fingerprint image pickup unit, 42 an in-blockaverage luminance calculation unit, 43 a luminance deviation calculationand arrangement unit, 44 a fingerprinting judging unit, 45 a fingerprintidentification unit, 46 an interface, 47 a binarizing unit, and 48 amemory. The fingerprint image pickup unit 41 comprises the camera 71,the light source 72, the prism 73 and the elastic film 74 as shown inFIG. 20.

A multivalued signal from the fingerprint image pickup unit 41 isconverted into a digital signal by, for example, the interface 46 andadded to the in-block average luminance calculation unit 42. Thein-block average luminance calculation unit 42, the luminance deviationcalculation and arrangement unit 43, and the fingerprinting judging unit44 can be a logical circuit having respective functions, but can also beachieved easily by a processor function provided by a microprocessor orthe like.

FIG. 11 is a flowchart of one embodiment according to the invention, inwhich steps (a) to (f) show an operation of judging fingerprinting.Description will be made with reference to FIG. 10 in addition to FIG.11. A multivalued image taken by the fingerprint image pickup unit 41 iscaptured through the interface 46 (a), and each in-block averageluminance in the judging area is calculated by the in-block averageluminance calculation unit (b).

For example, when it is assumed that an image pickup area 49 shown inFIG. 12 has 512×512 picture elements, a judging area 50 in the imagepickup area 49 can have, for example, 400×320 picture elements, and thejudging area 50 is divided into a plurality of blocks 51. Each block 51can have 16×16 picture elements, for example.

In the same way as described above, when it is assumed that the numberof blocks 51 in the judging area 50 is j, the number of picture elementsin the block is m, and luminance of the picture elements in the judgingarea is Pqn, in-block average luminance A q can be determined by theexpression (1). As described above, when the number of picture elementsin the judging area 50 is 400×320 and the number of picture elements inthe block 51 is 16×16, then j=500 and m=256.

After determining the in-block average luminance (b), a differencebetween the luminance of each picture element and the each in-blockaverage luminance is determined, and the number of picture elementswhich have the same difference is determined (c). In other words, thedeviation between the in-block average luminance A q and the luminancePqn of each picture element in the block is determined by the luminancedeviation calculation and arrangement unit 43 and the deviation of allpicture elements in the judging area 50 is determined, therebydetermining the number of picture elements having the same deviation.

And, distribution of picture elements with respect to the deviation isdetermined with the deviation on the horizontal axis and the number ofpicture elements on the vertical axis. In other words, the number ofpicture elements having the same deviation is accumulated by theluminance deviation calculation and arrangement unit 43, and the numberof picture elements is arranged with respect to the deviation in a tableor the like. FIG. 13 shows one example of the distribution of pictureelements with respect to the deviation, in which curve A indicates astate that external light has entered, and curve B indicates a state offingerprinting. Specifically, when external light enters, the respectiveblocks 51 in the judging area 50 have almost the same luminance, so thatthe number of picture elements in the neighborhood of deviation zeroincreases. Therefore, a unimodal characteristic is indicated. Ideally,when the luminance in the judging area 50 is uniform, the number ofpicture elements with deviation zero is 128000 in the above-describedcase, and the number of picture elements with other deviation is zero.Thus, since the state of not fingerprinting shows the unimodalcharacteristic, when a threshold is determined to be the number ofpicture elements exceeds the threshold σ.

And, when a fingerprint is pictured, the luminance distributioncorresponds to very small patterns of ridge and valley lines of thefingerprint, and the number of picture elements in the neighborhood ofdeviation zero is relatively decreased. Specifically, the pictureelements having the luminance same as the in-block average luminancedecreases, the picture elements are distributed to correspond to thedeviation over a relatively broad area of deviation, and a bimodalcharacteristic is indicated which shows that the number of pictureelements is maximum at a certain value of deviation + or deviation -. Insuch a case, the maximum number of picture elements does not exceed thethreshold σ.

As to the actual relation between the deviation and the number ofpicture elements, the maximum value of the curve A or the valley of thecurve B does not conform with the position of deviation zero because ofthe properties of the fingerprint image pickup unit 41, the transfercharacteristics in the interface 46 or the like, and the digitizingcharacteristics of the multivalued image signal. Accordingly, a range of±β is determined with a point shifted from the point of deviation zeroin the direction of the horizontal axis by a prescribed value a as thecenter, and the number of picture elements within the range is examinedto be greater than the threshold a (step (d) in FIG. 11). FIG. 13 showsa sate of shifting in the direction of negative deviation from thedeviation zero, but it may shift in the direction of positive deviationdepending on the characteristics of each unit. And, the value of ±β isselected in view of the shapes of curves A and B, and determined toinclude a range where the number of picture elements in the neighborhoodof deviation zero of the curve B is small and a range where the numberof picture elements in the neighborhood of deviation zero of the curve Ais many, so that a judgment error can be decreased.

And, it is judged whether or not the range of ±β includes any number ofpicture elements exceeding the threshold σ (step (e) in FIG. 11), and ifany number of picture elements exceeding the threshold σ is contained,it means that fingerprinting is not made and external light is entering,the process goes to step (a); and if no number of picture elementsexceeding the threshold σ is contained, it is judged that fingerprintingis made, and (f) the fingerprint is registered and identified.Specifically, step (e) is performed by the fingerprinting judging unit44, and when it is judged that fingerprinting is made, binarization ismade in the binarizing unit 47, the fingerprint is registered into thememory 48 when registering, and the registered fingerprint is read fromthe memory 48 when identifying and identified in the fingerprintidentification unit 45, and identification judgment output ofidentifying or not of the person in question can be obtained.

INDUSTRIAL APPLICABILITY

According to the dictionary image renewing method in the fingerprintidentification device of the present invention, time of period requiredfor dictionary identification can be shortened, and an identificationmatch rate can be prevented from lowering due to the cancellation of theidentification processing because of the continuous occurrence ofmismatching with the minutia data.

According to the dictionary image renewing method in the fingerprintidentification device of the present invention, the registereddictionary images can be renewed to keep the best dictionary images, sothat the fingerprint identification device can keep a highidentification rate. Therefore, the present invention performs greatservices to improve the reliability of the fingerprint identificationdevice.

According to the multiple dictionary registration and registrationmethod in the fingerprint identification device of the presentinvention, an identification rate can be improved by registering aplurality of dictionaries to identify, and at the time of registeringthe dictionary image, more stable multiple dictionary images can beobtained readily, and at the time of identifying, the identificationprocessing with the multiple dictionaries can be made readily. Thus, theinvention performs great services in improving the performance of thefingerprint identification device.

According to the fingerprinting judging method in the fingerprintidentification of the present invention, a continuous state thatfingerprints are judged as rejection is prevented, and timing ofcapturing the fingerprint image after fingerprinting is made constant,and the capturing can be made in a short time after fingerprinting.Thus, the invention performs great services in improving theidentification rate of the fingerprint identification device.

The fingerprint identification device and the fingerprinting judgingmethod of the present invention comprises the fingerprint image pickupunit, the in-block average luminance calculation unit, the luminancedeviation calculation and arrangement unit, the fingerprinting judgingunit and the fingerprint identification unit; deviation between eachin-block average luminance and the luminance of each picture element inthe judgment area is determined, the number of picture elements havingthe same deviation is determined, it is judged whether or not the numberof such picture elements exceeds the threshold, and if not, it is judgedto be a fingerprinting state, and identification of the fingerprint isperformed; when it is not a fingerprinting state and intense externallight enters or nothing enters, the number of picture elements in theneighborhood of deviation zero increases, so that it is advantageousthat the fingerprinting state can be judged with reliability, and inaddition to the time of identifying the fingerprint, it can be judgedwhether the fingerprint has been read accurately at the time offingerprint registration.

And, in the fingerprint identification device comprising the fingerprintimage pickup unit, the in-block average luminance calculation unit, theluminance deviation calculation and arrangement unit and thefingerprinting judging unit, when deviation between the averageluminance of every multiple blocks in the judging area and the luminanceof the picture elements in the block is determined and the deviation isindicated on the horizontal axis and the number of picture elementshaving the same deviation on the vertical axis, it is judged as afingerprinting state when the number of picture elements within therange of ±β does not exceed the threshold σ with the point shifted fromthe point of deviation zero in the direction of the horizontal axis by aprescribed value α as the center, and the number of picture elementswithin the range is examined to be greater than the threshold σ, so thatit is advantageous that the fingerprinting state can be judgedaccurately by selecting the shift value α and the judging area βaccording to the characteristics of each unit.

What is claimed is:
 1. A dictionary image renewing method in afingerprint identification device which registers images into adictionary memory as multiple dictionaries, the method comprisingextracting images from a plurality of fingerprint images determined asbeing acceptable identification by mutual identification and using saidmultiple dictionaries to perform identification processing of enteredfingerprint images, including successively identifying by comparingentered fingerprint images with the dictionary images registered in saidmultiple dictionaries, and when identification acceptance results withany one of the multiple dictionaries, the one dictionary determined asbeing identification accepted being renewed to the dictionary imageregistered in any one of the remaining dictionaries, and said remainingmultiple dictionaries being renewed to the dictionary image extractedfrom said entered fingerprint images.
 2. A dictionary image renewingmethod in a fingerprint identification device which registers imagesinto a dictionary memory as multiple dictionaries, the method comprisingextracting images from a plurality of fingerprint images determined asbeing acceptable identification by mutual identification and using saidmultiple dictionaries to perform identification processing of enteredfingerprint images, including successively identifying by comparing theentered fingerprint images with the dictionary images registered in saidmultiple dictionaries, and when identification acceptance results withthe multiple dictionaries, the dictionary determined as resulting inidentification acceptance being renewed to the dictionary imageregistered in any one of the other dictionaries, and said any one of theremaining dictionaries being renewed to the dictionary image extractedfrom said entered fingerprint images; and when identification acceptanceresults with the dictionary determined as resulting in identificationacceptance, and rejection results with any one of the remainingdictionaries, the dictionary resulting in said rejection being renewedto the dictionary image extracted from said entered fingerprint images.3. A dictionary image renewing method in a fingerprint identificationdevice which registers images into a dictionary memory as multipledictionaries, the method comprising extracting images from a pluralityof fingerprint images determined as being acceptable identification bymutual identification and using said multiple dictionaries to performidentification processing of entered fingerprint images, includingsuccessively identifying the entered fingerprint images by comparing theentered fingerprint images with the dictionary images registered in saidmultiple dictionaries, and when identification results in acceptancewith any dictionaries, dictionaries other than the dictionary made bythe fingerprint image first registered into said multiple dictionariesbeing renewed to the dictionary image extracted from the enteredfingerprint images.
 4. A dictionary image renewing method in afingerprint identification device the method comprising: registeringdictionary images extracted from multiple fingerprint images which havebeen judged as acceptance by mutual identification as a main dictionaryand a sub-dictionary in a dictionary memory and using said maindictionary to perform identification processing of an enteredfingerprint image, including when identifying the entered fingerprintimage with said main dictionary, also identifying with thesub-dictionary to renew an identification match rate of each dictionary,and replacing said sub-dictionary by said main dictionary when theidentification match rate of the sub-dictionary exceeds theidentification match rate of the main dictionary.
 5. A multipledictionary registration and identification method in a fingerprintidentification device having a binary memory for holding a binarizedinput fingerprint image, a minutia extracting means for extractingminutia from said binarized fingerprint image, a dictionary memory forregistering said extracted minutia as dictionary images, anidentification memory for holding minutia to be identified, and anidentifying means for identifying the finalized image held in saidbinary memory with the minutia held in the identification memory,wherein the method comprises: mutually identifying a plurality offingerprint images on the same finger at the time of registering thedictionary image, identifying the minutia of the fingerprint image asacceptance and registering in said dictionary memory as a dictionaryimage the minutia identified as accepted, and at the time of identifyingthe entered fingerprint, registering in said dictionary memory asdictionary image the entered fingerprint image identified as accepted,and at the time of identifying the entered fingerprint, identifying theentered fingerprint image with said dictionary images, and whenidentification with any dictionary image results in acceptance, judgingthe input fingerprint as identification success.